December 12, 2002


Urban Heat Island Effect and Countermeasures

Keywords: Climate Change Ecosystems / Biodiversity Government Others 

Japan's Ministry of the Environment recently released the results of research on the "heat island effect." This phenomenon has become noticeable in large cities in recent years, and is attributed to the presence of man-made ground surfaces such as asphalt or concrete and to the increase in man-made heat emissions, from air-conditioners, office equipment and automobiles.

For example, out of Tokyo's 23 wards (86,982 hectares of land area), buildings cover 26.6 percent of the land, and asphalt road and other surfaces cover 26.3 percent.

Consequently the heat energy which directly warms the atmosphere has increased by as much as 80 percent, when compared with "natural conditions" with tree cover. As a result, during the 20 years from 1980 to 2000, the cumulative hours exceeding 30 degrees Celsius from July through September doubled in Tokyo and Nagoya, and tripled in Sendai.

The heat island effect brings about various impacts on human health such as heat-caused disorders and insomnia, on natural habitats such as the timing of plant flowering, and on electricity consumption, which is pushed up in the summer by the increasing use of air-conditioning. As an example, if the temperature goes up by one degree Celsius in Tokyo Electric Power Company's service areas (Tokyo and eight surrounding prefectures), the maximum power consumption at peak times increases by 1.66 million kilowatts.

The following countermeasures against the heat island effect, known as "atmospheric heat pollution," are being considered: (1) effective utilization of natural wind and water surfaces, (2) reduction of heat emissions from buildings and automobiles by energy-saving efforts, (3) greening of ground surfaces, rooftops, and wall surfaces, and (4) paving the roads with water-retaining materials. The perspective of "heat management," including heat dissipation is, now essential to manage the heat balance of the entire city.

Posted: 2002/12/12 12:02:42 PM
Japanese version